An initial background check performed on Gary Martin in 2014 failed to catch a 1995 felony conviction for aggravated assault that would have barred the Aurora, Ill. gunman from purchasing a firearm.

Martin, who police say killed five people and wounded several others at an Aurora warehouse facility on Friday, reportedly passed the background check in January 2014 and was subsequently issued a firearm owner’s identification card.

According to Aurora police chief Kristin Ziman, Martin used the card to purchase a Smith & Wesson .40-caliber handgun two months later. It wasn’t until he applied for a concealed carry permit five days later that the felony was flagged, thanks to what AP described as “vetting using a more rigorous digital fingerprinting system.”

Martin ignored a letter from Illinois State Police demanding he surrender the weapon, CNN reported. It was unclear why law enforcement did not follow up to obtain the gun. “He was not supposed to be in possession of a firearm,” said Ziman.

Police say the 45-year-old ex-Henry Pratt Co. employee stormed into the facility on Friday and fatally shot five employees, including its human resources manager and a plant manager. He also wounded a sixth worker along with five police officers who responded to the shooting.

Police eventually killed the shooter.

The shooting sparked many liberals, from Chelsea Clinton to Chris Murphy, to tweet calls for more gun control, including “universal background checks” and an “assault weapons ban.”

100 people die from guns every day. That’s a national emergency.

If Trump gets away w this border emergency declaration, then a Dem President can declare a gun violence emergency and institute universal background checks and an assault weapons ban by executive action.